In aged cats a series of interdisciplinary studies will be carried out with the objective of defining changes in sleep and wakefulness due to the aging process as revealed by correlated behavioral, electrophysiological and neuroanatomical techniques. The circadian distribution of sleep and waking states and the attendent patterns of electroencephalographic, electroocular, electromyographic, cardiac and respiratory activity will be examined. These data will be individually analyzed and cross-correlated to generate a comprehensive behavioral and electrophysiological profile of state-dependent patterns of neural activity. Combined light (Golgi) and electron microscopic analysis of the neural substrates for the behavioral and electrophysiological data obtained during sleep and wakefulness will be carried out to provide a comprehensive description of the regulation of state-dependent processes in the aging feline brain.